The mechanical processing of thermoplastic synthetic materials, available in the form of pieces, granulate, chips, grains and the like, to a powdery synthetic material by using suitable comminuting machines, such as cutting machines, carving machines and mills, is in many respects complicated and expensive. With decreasing particle size also increases the power necessary for continuous comminution, so that even with relatively considerable power input and the use of efficient machines, only very slowly can be achieved the decrease in the particle size. This is very undesirable when substantial amounts of a finely distributed powder are to be produced from a thermoplastic synthetic material, available in much coarser form.